London: High doses of two common painkillers, used by millions of Indians, taken over a long period of time may increase the risk of heart attack, Oxford researchers have warned.

The study on more than 3,50,000 patients taking prescription doses of such medications found the chance of a heart attack or stroke rose by almost 40 percent.

The study found the increased risk of cardiac side-effects from ibuprofen was similar to those of another arthritis drug, Vioxx, which was withdrawn from the market almost a decade ago when research had suggested it might double the risk of heart attacks, a daily reported.

The University of Oxford study findings suggest prolonged use of non-steroidal anti-inflammatory drugs (NSAIDs) and taken by millions of arthritis sufferers ‘risky’ but said patients needed to weigh up the benefits of drugs which allowed them to function against the potential dangers.

The research, published in The Lancet, found that for every 1,000 people with a moderate risk of heart disease, around eight would normally have a heart attack or stroke each year.

When similar patients were given one year of treatment with a high dose of ibuprofen (2400mg daily) or diclofenac (150mg daily) that risk rose, with 11 patients suffering the major cardiac events. The study found one in three of the extra heart attacks were fatal.

The same dosage - which is the maximum normally prescribed, and twice the amount which is allowed over the counter - doubled the risk of heart failure, from 3 to 7 cases in 1,000, and more than doubled the risks of complications such as bleeding ulcers, the study found.

However, the findings, from an analysis of 639 randomized trials, found that a third drug, called naproxen, did not increase the risk of heart attacks or strokes, when a high dose of 1000 mg a day was taken.